lesbian vs homosexual

lesbian and homosexual both are nouns.

Word	Noun	Adjective	Verb	Adverb
lesbian	Yes	Yes	No	No
homosexual	Yes	Yes	No	No

As nouns, homosexual is a hypernym of lesbian; that is, homosexual is a word with a broader meaning than lesbian:

Other hypernyms of lesbian include gay, homo, homophile, adult female, woman.

lesbian (noun)	homosexual (noun)
a female homosexual	someone who is sexually attracted to persons of the same sex

lesbian (adjective)	homosexual (adjective)
of or relating to or characterized by homosexual relations between woman	sexually attracted to members of your own sex